Cementitious compositions are used in a number of applications which demand materials that function over a wide range of environmental conditions. As one example, cementitious compositions are commonly used to seal wellbores in oil and gas drilling. A composition selected for this application supports the casing of the well and provides zonal isolation in the annular region surrounding the casing and adjacent geologic formations. Such compositions operate under relatively severe conditions, including extremes of temperature and pressure.
Cementitious compositions for oil well applications are maintained in a fluid state during the period in which the composition is pumped. After pumping, the composition begins to set and eventually hardens to a suitable strength. If the setting time is short, the composition hardens rapidly and oil extraction may commence more quickly. Thus, cementitious compositions for oil well applications should generally exhibit low initial viscosity, suitable pumpability, and short setting times once the compositions are in place surrounding the well annulus.
The oil and gas industry has defined standards for various classes of cement used in wellbore applications. The American Petroleum Institute (API) specifies Classes A through H. Class H cement is specified as applicable for more challenging applications involving deep wells (down to 8,000 ft). The performance requirements for oil wells generally preclude the use of relatively inexpensive cementitious compositions commonly used in less demanding applications. These relatively inexpensive cements may include, for example, API Classes A through F cements as well as Types I, II and III cements defined by the American Society for Testing and Materials (ASTM).